Field-effect transistor

BIPOLAR TRANSISTORS BEHAVE AS BECAUSE CURRENT VARIATIONS AT one P-N junction produces larger current variations at the other. You have seen a simplified picture of how this take place, and how this effect can be exploited to get current amplification.The bipolar transistor is not the only way by which semiconductors can be combined to obtain amplification effects. The other major category of transistor, besides the bipolar device, is field-effect transistor or FET. There are 3 basic types of FET: the junction FET (JFET) and metal-oxide FET (MOSFET).